Selective hydrogenation of nu-substituted aziridines



United States Patent 3,242,165 SELECTIVE HYDROGENATION 0F N-SUBSTI- TUTED AZIRIDINES George E. Ham, Lake Jackson, and Prella M. Phillips,

Angleton, Tex., assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed June 8, 1964, Ser. No. 373,487

Claims. (Cl. 260-239) 1 This invention relates to a process for the manufacture of N-alkyl aziridine compounds by the selective catalytic hydrogenation of N-alkenyl aziridines.

The hydrogenation of N-substituted aziridinyl compounds which contain a reducible substituent (such as a cyano group) with Raney nickel as a catalyst has been reported by Bestian in Ann. Chemie, vol. 566, pp. 2l0-244 (1950). With other N-substituted aziridines (such as a sulfonyl group), the cleavage of the aziridine ring is almost complete as disclosed by Kharasch et al. in J. Amer. Chem. Soc., 61, 2425 (1939).

It has now been found that N-alkenyl aziridines may be selectively reduced to the corresponding N-alkyl aziridine compounds with a minimum of cleavage of the heterocyclic ring by contacting the N-alkenyl aziridine with hydrogen in the presence of a platinum, rhodium, ruthenium or palladium metal catalyst. Mixtures of these metals in finely divided form may also be used. The catalysts may be used with or Without a suitable support such as alumina, silica, diatomaceous earth or other inert material.

When the hydrogenation of an N-alkenyl aziridine is carried out in the presence of Pt, Pd, Ru or Rh metal, the reduced product obtained generally contains from 80 to 99.5 percent by weight of the corresponding N-alkyl aziridine compound. Reduced products of especially high purity (90-995 percent) are obtained with platinum and ruthenium catalysts.

The process of the invention is carried out by placing the N-alkenyl aziridine compound in a suitable pressure vessel with from about 0.005 to 15.0 percent by weight of metallic Pt, Rh, Ru or Pd (supported or unsupported) and maintaining the mixture at a temperature of from about to 200 C. (preferably from 25 to 100 C.) under a pressure of somewhat less than atmospheric up to about 5,000 p.s.i.g. for a time period sufiicient to obtain complete reduction of the N-alkenyl aziridine compound. Time periods of from 1015 minutes up to about 4 8 hours are generally sufiicient under the stated process conditions of temperature and pressure. With platinum metal as the catalyst, the reduction may be carried out at temperatures of from to 110 C. under pressures of from p.s.i.g. to 2,000 p.s.i.g. With ruthenium and/or rhodium, temperatures of from 25 to 75 C. and pressures of from 25 p.s.i.g. to 2,000 p.s.i.g. give good results.

One of the advantages of the process of the invention is that the reduction reaction may be carried out with excellent yields and high conversions Without the use of a solvent. Solvents may be used in the present process, but are not desirable from the engineering standpoint because an extra separation step is required when solvents are employed.

Patented Mar. 22, 1966 The reaction upon which the process of the invention is based may be represented by the following equation wherein R is a monovalent olefinic hydrocarbon group of from 2 to 8 carbon atoms which contains no acetylenic or aromatic unsaturation (groups such as a vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl or octenyl group are suitable), R is a corresponding alkyl group of from 2 to 8 carbon atoms (such as an ethyl, n-propyl, n-butyl, i-butyl, sec.-butyl or a pentyl, hexyl, heptyl or octyl group and the corresponding isomers) and each R group is the same or a difierent lower alkyl group or a hydrogen atom. Illustrative reactions which may be carried out according to the process of the invention include the following:

The following examples are submitted for the purpose of illustration only and are not to be construed as limiting the scope of the invention in any way.

EXAMPLES IXI.GENERAL METHOD A 40.25 gram sample of N-allyl aziridine was placed in a suitable pressure vessel along with 0.5 gram of the appropriate catalyst. No solvent was employed. The charged vessel was pressured with hydrogen and the temperature controlled until hydrogen uptake ceased. The process variables and results are summarized in Table l.

dine which comprises contacting N-(alIyDaZIridine With hydrogen at a pressure of from 25 p.s.i.g. to 2,000 p.s.i.g.

We claim as our invention:

and a temperature of from to 110 C. in the presence 1. A method of selectively hydrogenating a compound of metallic platinum.

of the formula 4. A process for the preparation of N-(n-propyl)aziridine which comprises reducing N-(allyl)aziridine with hydrogen in the presence of ruthenium metal at a temperature of from 25 to 75 C. under a pressure of from 25 p.s.i.g. to 2,000 p.s.i.g.

5. A process of preparing N-(n-propyl)aziridine by reducing N-(allyl)aziridine with hydrogen without substantially cleaving the aziridine ring which comprises contacting said N-(allyl)aziridine with molecular hydrogen in the presence of rhodium metal at a temperature of from 25 to 75 C. under a pressure of from 25 p.s.i.g. to 2,000 p.s.i.g.

References Cited by the Examiner Ellis: Hydrogenation of Organic Substances (New York, 1930), pages 87-88.

Lasselle et al.: J. Am. Chem. Soc., vol. 63, pages 2374- 2376 (1941).

NICHOLAS S. RIZZO, Primary Examiner. 

1. A METHOD OF SELECTIVELY HYDROGENATING A COMPOUND OF THE FORMULA 